In the manufacturing of semiconductor devices, integrated circuit dies are formed on a wafer and then separated from the wafer using a saw. Generally, sufficient space is left between adjacent dies to allow for the width of a saw blade during cutting. This space between the dies is referred to as a scribe line, and usually contains test structures used to verify the properties of the die.
Unfortunately, the physical process of sawing the wafer may damage the physical structure of the dies. For example, the saw could crack the silicon crystal of the wafer, and these cracks could then propagate through the dies. The saw may also cause a partial or complete delamination of the dies, essentially pulling off some of the layers that have been deposited onto the wafer. Additionally, the test structures, which could be located in the scribe line itself, can also cause cracking when the die is cut. Damage such as this would render the dies unusable and ruin the commercial value of the dies.
One attempt to contain cracks and delamination is to use dummy metal structures in the scribe line. These dummy metal structures are normally used to balance the metal density during chemical mechanical polishing (CMP). However, when they are used appropriately, they can act as a precipitate in order to stop dislocation movement, and prevent cracks and delamination from spreading. These dummy metal structures could be placed all around the die, or else they could be placed in areas where potential cracking would be concentrated, such as the corners of the die.
In cross section, the dummy metal structures can comprise various metal layers and vias in different dielectric layers over the semiconductor substrate. However, this form of dummy metal structure does not sufficiently protect the die from damage during the sawing process.